The invention relates to a casting device and a casting method for manufacturing or completing a cylinder head, respectively.
In gravity casting of cylinder heads, a comparatively heavy sand cover core of large volume in which a feeder system is integrated is conventionally used. The feeder system, inter alia, serves in compensating for shrinkage of the casting during cooling and for avoiding shrinkholes in the interior of the setting casting. In the manufacture of a cylinder head of a four-cylinder engine, the feeder system has a melt volume of about 14 kg, and in the case of 6-cylinder cylinder heads a melt volume of approx. 20 kg. The large amount of melt volume is required in order to ensure that the melt in the feeder is still liquid when the component to be produced has been completed. On account thereof, compensation via the feeder system for shrinkage may be ensured at all times. The feed system is conventionally surrounded by the sand cover core and, on account thereof, is also thermally insulated.
It is disadvantageous in the known solution that both components, feeder and sand cover core, have a heavy weight which has to be processed in the method. This leads to a large amount of circulating material and to long cycle times.
Against this background it is an object of the invention to provide a device by way of which components may be manufactured by gravity casting, without the previous large and heavy feeder systems which limit the cycle time in production that must be employed. It is furthermore an object of the invention to provide a method for manufacturing components of this type, in particular cylinder heads.
This and other objects according to the invention are achieved by a casting device and a casting method for producing components, in particular cylinder heads, having a reusable upper steel core which is liftable from the component to be produced and which has a movable displacement element. The displacement element is pressable into the component to be produced.
Here, provision is made for a casting device for producing components, in particular cylinder heads. The casting device has a reusable upper steel core which is liftable from the component to be produced and which has a movable displacement element which is pressable into the component to be produced. The sand cover core, having an integrated feeder system, which is used in the method according to the prior art, is entirely substituted by the upper steel core. A feeder system in the context of the prior art becomes obsolete. The upper steel core—instead of the previously used sand cover core—is placed onto the component to be produced and reproduces the surface contour of the latter as a negative. For dense feeding, a displacement element is pressed into the component to be produced which has not yet set (melt), on account of which the volume of melt in the displacement element is displaced. This displaced melt volume serves as a replacement for the melt which is otherwise added via the feeders. Dense feeding is thus performed using melt material which has been originally provided by the component to be produced per se. It may be provided here that a minutely increased processing addition in terms of melt material is provided on the upper flange faces.
In one favorable embodiment according to the invention, it is provided that the displacement element is disposed at a position of the upper steel core which correlates with a position of the component to be produced which, in a final state of the component to be produced, forms a clearance. Pressing the displacement element into the component to be produced is thus simultaneously a manufacturing step of a clearance in the component to be produced. In the manufacture of a cylinder head it is favorably provided that the position of the displacement element corresponds to the position of the spark-plug well of the cylinder head. The number of displacement elements in such a case depends on the number of cylinders of the cylinder head.
In the production of such a spark-plug well it is favorable that the displacement element is configured as a movable steel pin which is pressable into the melt of the cylinder head and there causes a cylindrical clearance.
In one embodiment it is furthermore provided that the displacement element is equipped with a cooling unit and/or heating unit. The cooling unit is configured in order for air, water, or oil as a coolant to be directed past the displacement element by way of internal ducts for example, so as to cool the displacement element. In one potential embodiment, a heating cartridge is integrated as a heating unit in the displacement element. The displacement element may be cooled and/or heated in this way, and the influence on the melt in the region of the displacement element may be selectively and individually adapted.
A method for manufacturing a cylinder head by the casting method is likewise part of the invention. As a substitute for a sand cover core, a reusable upper steel core is used. The steel cover core is liftable from the component to be produced and has a displacement element which, for dense feeding, is pressed into a melt which in the solidified state forms the cylinder head. It is provided according to the invention in the method that the displacement element is only pressed into the cylinder head after the melt has cooled off to the extent that an external skin has formed thereon. This is therefore favorable in that a wall shell is present on the sand core and the melt is not pressed into the sand core of the cylinder head.
The advantages of the device according to the invention and of the method according to the invention lie, in particular, in that the previously required sand cover core having an integrated feeder system is entirely replaced by a single upper steel core. The upper steel core according to the invention is capable of integration into the casting system, is reusable, and is liftable from the component to be produced. The feeder volume which is provided by the component to be produced per se corresponds to only 10 to 15% of the original volume which was previously provided in feeders. On account of the reduced melt volume, setting is more rapid and cycle times are shorter. Where the space which is displaced by the displacement element is utilized (for example as a spark-plug well), a subsequent machining process may be avoided.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
The figures are exemplary and schematic. Same reference signs refer to same parts in all figures.